Why doesn't the Terrains system just work similarly to RPGMaker's autotiles? It's far superior and gives much more control. I've already gone to the trouble of making my tilesets compatible with that method.

I really like Tiled, but the issue is that it lacks options. The way it's set up, I have to insert tiles 3x3 at a time, or 2x2 at a time, or if I want to have a 1 tile wide river, I have to do that manually, because Tiled wouldn't know what to do if I tried. However, with RPGMaker, it absolutely is equipped to handle it.

My suggestion is to add a brush style mechanic so users can choose to have a 1 tile wide option as well as the 2x2 and the 3x3.

I think both approaches to terrain transitions have their benefits. RPGMaker's version may appear to handle one-tile wide rivers, but since it works by first splitting up the tiles in even smaller pieces and then recombining them, it is not immediately clear how this could be implemented nicely in Tiled. In addition, that system is very specific to RPGMaker and outside of RPGMaker I've seen the majority of tilesets with such transitions using the system upon which the Terrain Brush is based.

Well, to be honest, the rivers example was simply that: an example. I had hoped to save time by using that as an example, but no worries.

The full reason I'd like to be able to have single-tile support is that it helps in making things less uniform. I can more easily do things like this for example:

(Done in RM2k3 because it looks a little nicer)

I take a lot of pride in making my maps look good, whether RPG or platformer, but don't want to spend a bunch of time doing that when there's a lot to do. (Which is obviously why I'm using Tiled instead of GameMaker's built in tile editor.)

I can't imagine it would be too terribly hard to change over to RPGMaker's style. Your system already kind of supports it. Instead of simply drawing terrain boundaries in colored highlights, you could have it set up to use symbols.

I used my own tileset as an example, here. Left: symbols overlaying the tileset. Center: the symbols themselves. Right: the tiles themselves. The way I see it working is, the user would define the structure of the terrain, much like it already does, by marking with symbols which piece represents what part of the terrain as a whole. The editor would start with the tile marked with the 1x1 tile symbol, and then adjust itself and its adjacent tiles accordingly while the user draws in their terrain. It would require a little more work on the user's part to have a tileset that supports the system, or alternatively, it could work both ways: current style and RPGMaker style, with use of a tickbox option. If that seems a little too slow to have users set up based on symbols, no problem: simply have an auto complete feature. The user would only need to set down one corner symbol or a middle symbol in each chunk, and then click a button and Tiled would fill in the rest of them to the best of its ability.